Method for dyeing and presetting tricot fabrics



Feb. 16, 1954 WALMSLEY 2,669,502

METHOD FOR DYEING AND PRESETTINGTRICOT FABRICS Filed July 16, 1951INVENTOR. L-ESL/E L. WALMSLEY BY W Arrai v.

Patented Feb. 16, 1954 OFFICE METHOD FOR DYEING AND PRESETTHNG TRICOTFABRICS Leslie L. Walmsley, Ridley-Park, Pa... assignor to AmericanViscose Corporation,

Wilmington,

DcL, a corporation of Delaware Application July 16, 1951, Serial No.236,912

(Cl. S 17) 3 Claims. 1

This invention relates to a method for simultaneously dyeing andpresetting, at full open width, tricot fabrics the edges of whichnormally tend to curl spontaneously during dyeing of the fabric.

Tricot fabrics have not been dyed at full open width heretofore because,as is wellknown, the selvages of a tricot fabric normally tend to curlor roll inwardly as much as a to 12 inches on either side of the fabric,when it is relaxed, and in order to prevent such curling during dyeingof thefabric it has been the practice to the edges of the fabrictogether before entering it into the dyebath. The precaution of sewingthe edges together prior to dyeing a tricot fabric in .a hot dyebath hasbeen particularly important in the case of fabrics of thermoplasticmaterials such as cellulose acetate since there it is necessary to avoidsetting of the edges in the curled condition by the heat of the bath inorder to avoid the waste of material which would result if the edgeswere set in the curled condition and the curled fabric hadto be cutaway.

It is obvious that although dyeing the tricot fabrics in tubularcondition prevents edge-rolling or curling thereof during the dyeingoperation, the need for sewing the edges together and then removing thestitches after the fabric has been dyed is time-consuming and expensive.

One object of the present invention is to provide a method for dyeing atricot fabric the edges of which tend to roll s ontaneously at full openwidth while simultaneously presetting the fabric in the flat. open widthcondition.

tendency of the edges of a tricot fabric to curl spontaneously as soonas the fabric is taken from the knitting machine is due to strains whichare introduced into the fabric by looping of the yarns upon the needlesduringlcnitting thereof. Since this tendency is inherent, it will.persist until the strains responsible for it are completely relieved.

Ey p-resetting-the tricot fabric as used. herein is meant that,simultaneously with dyeingthereof, the strains in the fabric which causethe edges to roll or curl spontaneously are relieved with elimination ofthe tendency of the edges to curl.

I have found that it is unnecessary to sew the edges of a tricot fabrictogether prior to dyeing it, if the dyeing is performed at full openwidth under conditions such that the strains responsible for theedge-rolling are permanently relieved. This is acccmp shed, inaccordance with the invention, by uncurling the edges of the tricotfabric having curled edges and which is to be dyed, then passing theuncurled fabric longitudinally through a dyebath which is also a settingor stabilizing bath for the fabric under conditions such that curling ofthe fabric edges is prevented until the strains in the fabric arerelaxed, after which the edges will no longer curl spontaneously to anyappreciable extent. During relaxation of the strains in the dyebath, thefabric, which is maintained in flat condition, picks up the dye from thebath and the fabric withdrawn from the bath is dyed to the desired colorand depth of shade and stabilized in the substantially fiat condition.

In practicing the invention, the tricotfabric in the dry condition andhaving curled edges which. is to be dyed is advanced continuously to andalong a path through the dyeing and setting bath under a tensionsufficient only to draw. the fabric through the bath. and as thefabrica'dvances to the path through the bath the edges thereof are uncurled,the fabricbein'g passed into the path in the uncurled condition and heldin that condition until it is dyed and stabilized or preset.

The fabric may be dyed and preset concurrently withthe dyeing bypassingit only once through a solution or dispersion of the selected dyein a partial solvent or swelling agent for the yarns. For example, atricot fabric of regenerated cellulose yarns may be dyed and preset .bypassing it through an aqueous solution of a direct dyestuff containing20 to 30% ofsodium hydroxide. In the case of tricot fabrics comprisingyarns of a thermoplastic materiaLihowever, it is preferred toydye andpreset the fabric using a hot aqueous solution or dispersion ,of theselected dyestulf, the heat .of the bathin ducing the relaxation of thestrains required for setting of the fabric in thefiat condition. .Thetemperature of the bath will dependbnlthe length of time required forthe fabric to pass through it but generally will not be less than F. norhigher than about 25 F. below the melting point of the yarns. Forexample, a tricot fabric comprising yarns of commercial secondaryc"ellulose acetate can be dyed and set by 'uncurling the edges of thefabric and passing the uncurled fabric through an aqueous'dispersion ofone of the available water-insoluble cellulose acetate type dyestuffs(known also as nispersol' type dyes) maintained at a temperature between180 F. and 212 F. when the time r-eauiredto pass the fabric through thebath is from 2 to 5 seconds. The bath maycontain one .orunlore oftheswelling agents, for example alcohol, which are commonly used asassistants of celluloseacetate. Also, substances Which-pen mit the useof higher operating temperatures, 1. .e. substances which increase theboilinggpoint of the bath may be used, and may be desirable in dyeingand presetting tricot fabrics of nylon or the like. Further, the dyeingand setting bath may contain small amounts of finishing or lubricatingagents for the fabric, or such agents be added to a cold water baththrough which the dyed and preset fabric is passed after it emerges fromthe dyeing and presetting bath.

The conditions of the treatment, including the concentration of thedyestuff in the bath and the temperature of the bath, are selectedtaking into account the shade it is desired to dye the fabric, thethickness of the fabric, the length of the bath, and the fact that therate at which the fabric is withdrawn from the bath must be correlatedwith the rate at which it is fed into the bath to insure free passage ofthe fabric through the bath without placing it under a tension whichwould inhibit relaxation of the strains therein.

Any suitable uncurling device may be used to uncurl the edges of thefabric as it passes into the dyeing and presetting bath. However, theuse of liquid jets or sprays for uncurling the fabric is to be avoidedin order to prevent the dyeing variations which would result fromwetting of portions of the fabric prior to its introduction into thedispersion of the dyestuff.

It is essential to the successful practice of the invention that theuncurling means is so lo cated with respect to the dyeing and presettingbath that the fabric enters the path through the bath inthe fiat,uncurled condition, and that the fabric be prevented from recurling inthe bath before the strains responsible for the curling are relieved.

The fabric may be prevented from recurling after it passes into the bathby providing a mem her or members having a width at least as great asthe width of the fabric and which define the path for the fabric andexert downward pressure on the fabric in the dyebath across the entirewidth thereof to prevent recurling of the edges, to keep the fabricsubmerged, and to assist in guiding it along a path through the bathconsisting of an initial portion downwardly inclined from the fabricentrance and extending to a depth of at least two inches below the topsurface of the dyebath, a generally horizontal portion extending fromthe initial portion along a substantially straight line at a depth of atleast two inches below the top surface of the dyebath, and an upwardlyinclined portion extending from the generally horizontal portion out ofthe dyebath. Thus, the uncurled fabric may be passed under a guide platehaving a width at least as great as the width of the fabric, which issupported generally horizontally in and below the level of the bath, andthe lower surface of which defines the upper side of the path for thefabric and prevents recurling thereof. Or two plates or equivalentsthereof may be generally horizontally supported one above the other inspaced relation in the bath to define a path for the fabric therebetweenhaving a depth greater than the thickness of the fabric but less thanthe depth which would permit curling of the fabric edges.

In the attached drawing,

Figure l is a view in perspective of apparatus for carrying out onepreferred embodiment of the invention;

Figure 2 is a section taken on line 11-11 of Fig. 1; and

Figure 3 is a cross-section through the curled 4 selvage of a tricotfabric showing the coils in the edge-roll or edge-curl thereof.

Referring to the drawing, there is shown a vessel 2 provided with aremovable cover 2a and containing a dyeing and presetting bath for thetricot fabric. Two guide plates 3 and 4 are supported generallyhorizontally in the vessel as shown. The plates, which in a specificembodiment of the invention are each 12 inches wider than the fabric,are disposed one above the other, in spaced relation, to provide aguideway or tunnel 5 of substantially uniform cross-section for thefabric below the level of the liquid. The distance between the adjacent,smooth fiat surfaces of the plates is sufficient to permit free passageof the fabric between them, but is insufficient to permit curling orrolling of the fabric edges. This distance may be varied, depending onthe thickness of the fabric. The smooth lower face of the upper plate 3defines the upper side of the path for the fabric through the bath; thesmooth upper surface of the lower plate 4 defines the lower side of thepath for the fabrics. The opposite ends of plate 3 are curved or flaredupwardly, and the opposite ends of plate 4 are curved or flareddownwardly to facilitate feeding of the fabric to the space between theplates and withdrawal of the fabric from the vessel, and to preventundue tension on the fabric as it is advanced through the bath.

The dry tricot fabric having curled edges is advanced longitudinally atopen width (with that face of the fabric which forms the inside face ofthe coils in the edge-curls facing upwardly as shown) to vessel 2 overthe driven feed roll 6 downwardly over the inclined guiding andsupporting surface 1, fed between the plates 3 and 4, withdrawn fromvessel 2 by the driven rolls 8 and 9, a guiding roll iii being supportedin the vessel ll containing cold water and supported between rolls 8 and9. As shown, the guiding and supporting surface I is a fiat, plate-likemember and both it and the guide plates 3 and 4 are made of any suitablematerial, preferably a polished metal such as stainless steel. Guidingsurface 1 extends into vessel 2 and is fixed in inclined relation tofeed roll 6 and the guideway or tunnel 5 between plates 3 and 4 so thatthe fabric passes from the guiding plate 7 directly into the tunnel 5.

In order to uncurl the edges of the fabric and maintain the fabric inthe uncurled fiat condition until it enters the guideway 5 in whichrecurling is prevented by the guide plates, jets of a gaseous fluidunder pressure are projected in opposite directions extending laterallyoutwardly from the central portion of the upper face of the fabricagainst the opposite edges of the fabric at successive points along thepath of travel of the fabric downwardly over guiding and supportingsurface i (see Fig. 2) to the guideway 5. For this purpose, as shown inthe drawing, two pipes or conduits I2 and I3, each provided with a rowof perforations it, are supported above and parallel to the guidingsurface I on the cross-bars i5 and It which are in turn supported on thestandards ll, i8 and I9, 29. Pipes I 2 and I3 are adjustablehorizontally on the cross-bars l5 and It by adjustment of the clamps orbrackets designated generally at 2|, and cross-bars l5 and It areadjustable vertically on the standards i1, i8 and iii, 2i respectivelyby adjustment of the clamps or brackets designated generally at 22. Airor other gaseous fluid under pressure is fed to pipes I2 and i3,

'7 prises the steps of continuously advancing the aforesaid fabric inthe dry condition longitudinally toward a dyebath at open widthdownwardly over a fiat, inclined supporting surface with that face ofthe fabric which forms the inside face of the coils in the edge-curlsfacing upwardly, said dyebath comprising an aqueous dispersion of awater-insoluble cellulose acetate dyestuff and a swelling agent forcellulose acetat and being maintained at a temperature between 180 F.and 212 F., uncurling the edges of the fabric advancing to the dyebathas it approaches and immediately before it enters the dyebath bycontinuously projecting air jets in opposite directions extendinglate-rally outwardly from the central portion of the aforesaid face ofthe fabric against the opposite edges of the fabric while it issupported on said supporting surface, continuously drawing thethus-advanced fabric with its edges uncurled in full open width onlyonce through the dyebath, exerting downward pressure on the fabric inthe dyebath across the entire width thereof to prevent recurling of theedges and to keep the fabric submerged therein, guiding the fabric alonga path therein consisting of an initial portion down wardly inclinedfrom the fabric entrance and extending to a depth of at least two inchesbelow the top surface of the dyebath, a generally horizontal portionextending from the initial portion along a substantially straight lineat a depth of at least two inches below the top surface of the dyebath,and an upwardly inclined portion extending from the generally horizontalportion out of the dyebath, the fabric during said drawing step beingunder a tension sufficient only to draw the fabric through said pathwhereby to provide free passage of the fabric through the dyebathwithout placing it under a tension which would inhibit relaxation of thestrains therein, and circulating the dyebath by continuously withdrawinga portion thereof adjacent the end from which the fabric is dischargedand introducing the portion withdrawn adjacent the end into which thefabric enters at a plurality of points distributed the full width of thedyebath adjacent the bottom thereof.

2. A method of simultaneously dyeing and stabilizing againstedge-curling a tricot fabric comprising yarns of cellulose acetate andhaving strains which cause the edges to curl which comprises the stepsof continuously advancing the aforesaid fabric in the dry conditionlongitudinally toward a dyebath at open width downwardly over a inclinedsupporting surface with that face of the fabric which forms the insideface of the coils in the edge-curls facing upwardly, said dyebathcomprising an aqueous dispersion of a water-insoluble cellulose acetatedyestuif and a swelling agent for cellulose acetate and being maintainedat a temperature between 80 F. and 212 F., uncurling the edges of thefabric advancing to the dyebath as it approaches and immediately beforeit enters the dyebath by continuously projecting air jets in oppositedirections extending laterally outwardly from the central portion of theaforesaid face of the fabric against the oppositc edges of th fabricwhile it is supported on said supporting surface, continuously drawingthe thus-advanced fabric with its edges uncurled in full open width onlyonce through the dyebath at a rate such that the time of passage of thefabric through the dyebath is of the order of five seconds, exertingdownward pressure on the fabric-in the'dyebath across the entire widththereof to prevent recurling of the edges and to keep' the fabricsubmerged therein, and guiding the fabric along a path thereinconsisting of an initial portion downwardly inclined from the fabricen-- trance and extending to a depth of at least two inches below thetop surface of the dyebath, a generally horizontal portion extendingfrom the initial portion along a substantially straight line at a depthof at least two inches below the top surface of the dyebath, and anupwardly inclined portion extending from th generally horizontal portionout of the dyebath, the fabric during said drawing step being under atension sufficient only to draw the fabric through said path whereby toprovide free passage of the fabric through the dyebath without placingit under a tension which would inhibit relaxation of the strainstherein.

3. A method of simultaneous1y dyeing and stabilizing againstedge-curling a tricot fabric comprising yarns of cellulose acetate andhaving strains which cause the edges to curl which comprises the stepsof continuously advancing the aforesaid fabric in the dry conditionlongitudinally toward a dyebath at open width downwardly over a flat,inclined supporting surface with that face of the fabric which forms theinside face of the coils in the edge-curls facing upwardly, said dyebathcomprising an aqueous dispersion of a water-insoluble cellulose acetatedyestuff and a swelling agent for cellulose acetate and being maintainedat a temperature between F. and 212 E, uncurling the edges of the fabricadvancing to the dyebath as it approaches and immediately before itenters the dyebath by continuously projecting air jets in oppositedirections extending laterally outwardly from the central portion of theaforesaid face of the fabric against the opposite edges of the fabricwhile it is supported on said supporting surface, continuously drawingthe thus-advanced fabric with its edges uncurled in full open width onlyonce through the dyebath, exerting downward pressure on the fabric inthe dyebath across the entire width thereof to prevent recurling of theedges and to keep the fabric submerged therein, and guiding R the fabricalong a path therein consisting of an initial portion downwardlyinclined from the fabric entrance and extending to a depth of about twoinches below the top surface of the dyebath, a generally horizontalportion extending from the initial portion along a substantiallystraight line at a depth of about two inches below the top surface ofthe dyebath, and an upwardly inclined portion extending from thegenerally horizontal portion out of the dyebath, the fabric during saiddrawing step being under a tension sufiicient only to draw the fabricthrough said path whereby to provide free passage of the fabric throughthe dyebath without placing it under a tension which would inhibitrelaxation of the strains therein.

LESLIE L. WALMSLEY.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,913,601 Leppin June 13, 1933 2,303,934 I-Ieckert Dec. 1,1942 2,365,931 Benger Dec. 26, 19% 2,402,621 Gifford June 25, 19462,613,521 Walmsley Oct. 14, 1952 2,613,522 Heffelfinger Oct. 14, 1952 vOTHER REFERENCES Journal Textile Institute, page A253, May 1950. "RayonTextile Monthly, July 1944, page 325.

1. A METHOD OF SIMULTANEOUSLY DYEING AND STABILIZING AGAINSTEDGE-CURLING A TRICOT FABRIC COMPRISING YARNS OF CELLULOSE ACETATE ANDHAVING STRAINS WHICH CAUSE THE EDGES TO CURL WHICH COMPRISES THE STEPSOF CONTINUOUSLY ADVANCING THE AFORESAID FABRIC IN THE DRY CONDITIONLONGITUDINALLY TOWARD A DYEBATH AT OPEN WIDTH DOWNWARDLY OVER A FLAT,INCLINED SUPPORTING SURFACE WITH THAT FACE OF THE FABRIC WHICH FORMS THEINSIDE FACE OF THE COILS IN THE EDGE-CURLS FACING UPWARDLY, SAID DYEBATHCOMPRISING AN AQUEOUS DISPERSION OF A WATER-INSOLUBLE CELLULOSE ACETATEDYESTUFF AND A SWELLING AGENT FOR CELLULOSE ACETATE AND BEING MAINTAINEDAT A TEMPERATURE BETWEEN 180* F. AND 212* F., UNCURLING THE EDGES OF THEFABRIC ADVANCING TO THE DYEBATH AS IT APPROCHES AND IMMEDIATELY BEFOREIT ENTERS THE DYEBATH BY CONTINUOUSLY PROJECTING AIR JETS IN OPPOSITEDIRECTIONS EXTENDING LATERALLY OUTWARDLY FROM THE CENTRAL PORTION OF THEAFORESAID FACE OF THE FABRIC AGAINST THE OPPOSITE EDGES OF THE FABRICWHILE IT IS SUPPORTED ON SAID SUPPORTING SURFACE, CONTINUOUSLY DRAWINGTHE THUS-ADVANCED FABRIC WITH ITS EDGES UNCURLED IN FULL OPEN WIDTH ONLYONCE THROUGH THE DYEBATH, EXERTING DOWNWARD PRESSURE ON THE FABRIC INTHE DYEBATH ACROSS THE ENTIRE WIDTH THEREOF TO PREVENT RECURLING OF THEEDGES AND TO KEEP THE FABRIC SUBMERGED THEREIN, GUIDING THE FABRIC ALONGA PATH THEREIN CONSISTING OF AN INITAL PORTION DOWNWARDLY INCLINED FROMTHE FABRIC ENTRANCE AND EXTENDING TO A DEPTH OF AT LEAST TWO INCHESBELOW THE TOP SURFACE OF THE DYEBATH, A GENERALLY HORIZONTAL PORTIONEXTENDING FROM THE INITIAL PORTION ALONG A SUBSTANTIALLY STRAIGHT LINEAT A DEPTH OF AT LEAST TWO INCHES BELOW THE TOP SURFACE OF THE DYEBATH,AND AN UPWARDLY INCLINED PORTION EXTENDING FROM THE GENERALLY HORIZONTALPORTION OUT OF THE DYEBATH, THE FABRIC DURING SAID DRAWING STEP BEINGUNDER A TENSION SUFFICIENT ONLY TO DRAW THE FABRIC THROUGH SAID PATHWHEREBY TO PROVIDE FREE PASSAGE OF THE FABRIC THROUGH THE DYEBATHWITHOUT PLACING IT UNDER A TENSION WHICH WOULD INHIBIT RELAXATION OF THESTRAINS THEREIN, AND CIRCULATING THE DYEBATH BY CONTINUOUSLY WITHDRAWINGA PORTION THEREOF ADJACENT THE END FROM WHICH THE FABRIC IS DISCHARGEDAND INTRODUCING THE PORTION WITHDRAWN ADJACENT THE END INTO WHICH THEFABRIC ENTERS AT A PLURALITY OF POINTS DISTRIBUTED THE FULL WIDTH OF THEDYEBATH ADJACENT THE BOTTOM THEREOF.